The control of particle size, morphology or both is important in some circumstances. Particles size can be affected after production of the particles using processes such as milling, but such processes may have a detrimental effect on the material properties. During precipitation or crystallization from solution, particle size, morphology or other properties may be controlled.
Crystallization or precipitation is achieved by mixing a solvent containing an active principal to be crystallized with an anti-solvent, so that after mixing the solution is supersaturated and crystallization occurs. Precipitation can also be achieved by the reaction of two or more reagents that form a product which has reduced solubility in the solvents being used. The resulting insoluble reaction product precipitates or crystallizes from the solution. In such a situation, the solvents being used in the reaction would be considered to be anti-solvents with respect to the reaction product. The term “anti-solvent” means a fluid which promotes precipitation of the active principal from the solvent. The anti-solvent can be the same liquid as the solvent but at a different temperature, it may be a different liquid from the solvent, or (in the case of two reagents reacting to form a new product) it may be the solvent used in the reaction.
Ultrasonic irradiation (or sonication) has been used while precipitating or crystallizing particles. For example, Hussein OUBANI and others, in the Asia-Pacific Journal of Chemical Engineering 5 (2010) 599-608, describe the precipitation of NaCl microparticles from a NaCl—Ethanol—Water antisolvent system; L. BOELS and others, in the Journal of Crystal Growth 312 (2010) 961-966, describe the crystallization of a supersaturated calcite suspension under ultrasonic irradiation; and I. NISHIDA, in Ultrasonics Sonochemistry 11 (2004) 423-428, describes the ultrasonic irradiation of a supersaturated solution of calcium carbonate.
Hielscher Ultrasonics produces ultrasonic devices and describes an ultrasonic precipitation process at <http://www.hielscher.com/ultrasonics/precipitation—01.htm>.
A poster presentation by B. POHL, N. ÖZYLIMAZ, G. BRENNER, and U. PEUKER, entitled “Untersuchungen zur Optimierung von kontinuierlichen Ultraschalldurchflussreaktoren”, publically available at least as early as Dec. 20, 2010, describes how flow chamber size and geometry of ultrasonic reactors affect the formation of I3− and BaSO4.
A poster presentation by B. POHL, G. BRENNER, and U. PEUKER, entitled “Optimierung von Ultraschallfällungsreaktoren—kontrollierte Nanopartikelherstellung”, publically available at least as early as Dec. 20, 2010, teaches that ultrasonic precipitation reactors can be used to form agglomerations of Fe3O4 particles, where the agglomerates are between 20 nm and 300 nm (cavitation field reactor) or between 20 nm and 1 μm (conical reactor).
A review article discussing the chemical effects of ultrasonic irradiation was authored by Kenneth SUSLICK in Science 247:4949 (1990) 1439-1445. Another review article, by G. RUECROFT and others in Organic Process Research & Development, discusses the application of ultrasound to crystallization of organic molecules, and discusses equipment that could be used in industrial environments, such as parallel plate transducer systems.
Chunling LU and Jinglin ZHANG, in The Journal of the Chinese Ceramic Society 35:3 (2007) 377-380, describe subjecting a reaction of manganese sulfate (MnSO4) and ammonium bicarbonate (NH4HCO3) to ultrasonic irradiation, using an ultrasonic bath having an intensity of about 1 W/cm2, to form cubical manganese carbonate (MnCO3) particles from 400 to 500 nm.
Ting-Feng YI and Xin-Guo HU, in the Journal of Power Sources 167 (2007) 185-191, disclose preparing sub-micro spinel LiNi0.5−xMn1.5+xO4 (x<0.1) cathode materials with homogeneous particle size using an ultrasonic-assisted co-precipitation of LiNO3, Mn(NO3)2, and Ni(NO3)2.6H2O. The precipitation was sonicated at 80° C. for 5 h in an ultrasonic cleaner at 50 W and 28 kHz.
Peizhi SHEN and others, in the Journal of Solid State Electrochemistry (2005) 10:929-933, describe preparing a LiCrxMn2−xO4 (x=0, 0.02, 0.05, 0.08, 0.10) compound with spinel crystal structure using an ultrasonic co-precipitation method. Lithium acetate, manganese acetate, chromic nitrate and citric acid were dissolved in water and treated in an ultrasonic bath.
U.S. Patent App. No. 2010/0018853 describes the control of crystal and precipitate particle size of pharmaceutical drugs or other medicaments using ultrasonic irradiation.
Ultrasonic irradiation is also used in other processes for preparing particles. Tingfeng Y I, Xinguo H U and Kun G A O, in the Journal of Power Sources 162 (2006) 636-643, prepare Al-doped LiAl0.05Mn1.95O4 powders using an ultrasonic assisted sol-gel method, using adipic acid as a chelating agent. A sol-gel process is a wet-chemical technique used primarily for the fabrication of materials (typically a metal oxide) starting from a chemical solution (or sol) that acts as the precursor for an integrated network (or gel) of either discrete particles or network polymers. Stoichiometric amounts of reactants Li(CH3COO).2H2O, Al(NO3)3.9H2O and Mn(CH3COO)2.6H2O were used to prepare the LiAl0.05Mn1.95O4 powders.
S. H. PARK and others, in the Journal of Applied Electrochemistry (2003) 33: 1169-1173, describe the preparation of Li[Ni1/2Mn1/2]O2 using an ultrasonic spray pyrolysis method. In spray pyrolysis, the dissolved reagents are atomized using an ultrasonic nebulizer and the resulting aerosol stream is introduced into a heated reactor. They teach that stoichiometric amounts of Ni and Mn nitrate salts (cationic ratio of Ni:Mn—1:1) were dissolved in water and that the dissolved solution was added to a continuously agitated aqueous citric acid solution, which was used as a polymeric agent for the reaction. The starting solution was atomized using an ultrasonic nebulizer with a resonant frequency of 1.7 MHz and the aerosol stream was introduced into a reactor heated at 500° C.
In a similar process, S. H. PARK and others, in Electrochimica Acta 49 (2004) 557-563, teach the preparation of Li[Ni1/3Co1/3Mn1/3]O2 materials using a spray pyrolysis method, where citric acid is again used as a polymeric agent for the reaction.
Spherical particles can be used in the preparation of battery materials, as discussed by SUN and others in Process of Precipitation for Spherical Manganese Carbonate and Their Products Produced Thereby (WO 2006/109940), as well as in the pharmaceutical industry. Weijun TONG and Changyou G A O, in Colloids and Surfaces A: Physiochem Eng. Aspects 295 (2007) 233-238, describe the preparation of hollow spherical manganese carbonate capsules by the reaction of manganese sulfate and ammonium bicarbonate solutions to form manganese carbonate particles and then acid dissolution of the particle cores. Similarly, Alexei ANTIPOV and others, in Colloids and Surfaces A: Physiochem Eng. Aspects 224 (2003) 175-183, describe the formation of hollow capsules made using cadmium carbonate particles, manganese carbonate particles and calcium carbonate particles as core templates for adsorption of oppositely charged polyelectrolytes and subsequent core removal.
Although ultrasonic irradiation has been used during precipitation of metal compound particles, as described above, it is desirable to provide an ultrasonic irradiation-based method that allows for the production of particles with desired morphologies, desired size distribution and/or desired particle sizes.